A transition metal mediated approach to the synthesis of xestobergsterol-A and -B is described. The primary goals of the project are to: (1) synthesize xestobergsterol-A and xestobergsterol-B in enantiomericallypure form, (2) develop synthetic methods to solve problems that will inevitably arise, (3) provide a synthetic route that will permit access to derivatives for biological testing, (4) submit the intermediates for biological analysis, and (5) determine the functional groups necessary for biological activity. The approach to the synthesis of the xestobergsterols involves the use of a key transition metal mediated ene- yne cyclization to construct the bicyclo(3.3.0) portion of the molecule. Within the synthetic strategy, plans for the synthesis of the left hand portion and routes to the stereoselective synthesis of the right hand side of the ring system are described. The ultimate merger of the two approaches will lead to the synthesis of the xestobergsterols. The chemistry developed in the approach to the xestobergsterols should be applicable to the total synthesis of other molecules of biological interest